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What Does your Legionella Risk Assessment Score Mean?


A lot of scores can be incredibly difficult to try and work out if you’re not in the know. Take cricket for example, which makes absolutely no sense whatsoever should you not be a fan of the game. And let’s not even begin to think about how quidditch scoring works in reality. Thankfully, the scoring methodology surrounding Legionella risk assessments are a lot easier to fathom and explain to those not in the loop. Which is what we’ve tasked ourselves with here.

Broadly-speaking Legionella risk assessment scores can be divided into three core sections which reflect the acknowledged risk levels. This sliding scale of risk begins at the obvious starting point; that being low risk accreditation. Cutting through the body of details for the time being, this essentially means that the Legionella risk assessment has discovered that there is a negligible amount of revision needed at this juncture. In terms of points on the board, so to speak, we’re talking about a tally of anywhere between 0 – 15 accumulated. Which envelopes basic remedial work having been suggested by the assessor, once they’ve scrutinised a particular system in situ. They’ll also iterate that any further assessments will only need to be undertaken should a change in the system be actioned thereafter. This might include the accommodating of a new boiler, for example.

The Three key Legionella Risk Assessment Score Parameters

A Legionella risk assessment overview which results in a score of anywhere within the parameters of 16 – 40 points identifies that some, or possibly a significant amount of, remedial work needs to be rubber stamped and acted upon. Due to the scale of some sites which will be routinely visited by Legionella risk assessors, many won’t receive anything less than a medium risk classification, due to the volume of physical assets under the client’s governance. Structures such as tanks, calorifiers, showers, etc tend to fall into the bracket of medium risk by virtue of their potential to engender risk of contamination; thus being marked up as medium risk as very best. This scoring bears little significance to how compliant and scrupulous the client is, suffice to say, and is often purely based on working logistics. Meanwhile, high risk (41+ points) implies that a notable amount of remedial work needs to take effect in the immediate future, to ensure that the risk of contamination from the possible presence of Legionella is kept to a bare minimum.

Risk rating is predominantly based on a complex combination of factors, bolstered by our own, extensive real world competence and practical experience, coupled with a long-established knowledge set. And while the above briefly summarises just how legionella risk assessment scoring is manifest – in a nut shell – we now need to scratch more than the surface, and venture a little deeper to determine what, precisely the scoring system means. And moreover how you, the client, are expected to implement the necessary change flagged up.

Fundamentally – and irrespective of the final risk calculations at the end of our Legionella risk assessment – you can pretty much expect to implement some form of remedial work in the aftermath of our inspection, as rarely do businesses not have ways in which they can usher in improvements suggested to them, post-risk assessment. Which of course is always designed for the greater good, and do everything in your power to safeguard against the threat of legionella bacteria getting a foothold in your water storage system. And don’t forget, once the remedial works are satisfactorily completed in the intervening period between risk assessments, then the overall score will undoubtedly be lowered in the aftermath of the revisions and amendments being acted upon.

Can You Elaborate on These Remedial Actions Which Are Habitually Suggested After Legionella Risk Assessments Have Been Carried Out and Potential Threats Identified?

Yes. Based on the ramifications of your Legionella risk assessment, the following processes and procedures may need to be executed, depending on the preventative measures suggested and/or scale of individual set-ups/assemblages, and so as to reduce the risk of legionella exposure;

  • Dead end valves either removed or fitted, to allow weekly flushing. Failure to do this increases the risk of stagnant water becoming a breeding ground for legionella in such vicinities
  • Replacement of thermostatic mixing valves
  • Insulation fitments on storage vessels and pipework
  • Chlorination and disinfection of storage vessels and/or existing water systems per se
  • Re-configuration of cold water storage tanks
  • Proposed installation of cold water storage WRAS-approved lids, rodent screens and lid vents
  • Provision of legionella awareness and/or in-house task training.

Can You Give Examples/Accounts of Remedial Works Performed in These Situations?

Of course. It could be that the Legionella risk assessment discovered that single (or multiple) water storage tanks were showing signs of stagnation, hypothetically affecting both the inlet and outlet. If this was the case, such circumstances would necessitate the possible altering of fitting orientation, or alternatively reduce the tank capacity to minimise stagnation.

Elsewhere another good example might be the discovery of heavy deposits (or signs of corrosion) appearing on the storage tank. This would almost always signal the need to clean and disinfect said vessel ASAP. Meanwhile if a scenario such as an outlet that is used infrequently (and therein no flushing programme has been administered) is observed during an assessment, then the upshot would be that a well-established programme of running water through/flushing out the system would need to be agreed and upheld going forward.

And What About Timescales of Undertaking the Necessary Remedial Works, Based on the Degree of Risk Revealed at the Point of Risk Assessment?

Whilst any form of risk, be it large or small, shouldn’t ever be ignored, providing your assessment has flagged up a low risk then the call to arms isn’t as time-conscious as if you’d received a high risk report. But that’s not to say you can afford to rest on your laurels. An L8 compliance of management issue of any severity still needs to be rectified, and although the current status quo of your water storage system hasn’t been deemed a direct risk to public health, there’s still issues which require resolution. And achieving this end game at the earliest practical opportunity is in all party’s best interests, not least because it’s legally compliant. Reference-wise, this more often than not refers to a 6 month deadline for recommendation changes to have been effected.

Areas considered a moderate, or medium risk factor typically require addressing within 3 months of the problem being highlighted by the Legionella risk assessment, or as soon as is agreed to be practically applicable. Although from time to time this understanding can alter depending on any increased risk to the public’s health having been identified in the interim. If this is the case, then a high priority action is recommended, with a 1 month turn-around most likely to be dictated.

Should however the Legionella risk assessment scores be documented as falling into the high category, then timing is crucial. Not to put too finer point on it, we’re probably talking about both a significant and imminent threat being posed to public health, if immediate action isn’t sought.


The fact of the matter remains that the majority of clients’ water storage systems will need some level of revision at some point in their lives, the schedule of which will be determined after a thorough investigation has been carried out by our Legionella risk assessment experts. Our bespoke scoring system will ultimately confirm what extent of amendments to an existing system is recommended, on which it’s then over to the client to work with this information and effect the changes at their first opportunity.

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